Solution
Most cameras now come equipped with a convenient auto focus (AF) function which allows the camera to automatically focus on subjects without any manual focus adjustment being necessary.
It is a limitation of auto focus that some focus points may appear to shift when a picture is taken.
The AF focus accuracy of Canon Digital Single-Lens Reflex Cameras and Interchangeable-Lens Compact System Cameras is based on the principle that when a captured image is completely printed out and viewed at a distance appropriate to the print size, viewing it should be the same as viewing a photograph taken by a film camera.
However, when using digital cameras, it is easy to magnify or print out just a part of the image after it has been downloaded to your computer. Not printing the complete picture taken can magnify small errors in auto focus that would otherwise not be apparent when being viewed at a more traditional print size.
Tips for taking sharp and crisp images
Tips for taking sharper images are listed below.
1. Remember that AF may fail to focus on certain subjects – in such cases you are advised to focus on a different point of the subject (eg. an area with greater contrast) or to use manual focus (MF) adjustment instead – please refer to your product user manual for full instructions on how to use manual focus.
2. Take advantage of a deeper depth of field.
"Depth of field" is the range where acceptable focus is achieved in front of and behind the point of focus. The depth of field is changed by both the aperture and focal length of the lens. Using a deeper depth of field will help avoid getting images that are out of focus.
Keeping the aperture down (smaller aperture) makes the depth of field deeper.
If you use a zoom lens, move the zoom control towards wide-angle (shorter focal length) in order to get a deeper depth of field.
3. Shoot carefully without any camera shake.
If the camera shakes when shooting it may result in blurred images. Sometimes this may look like a focus problem when it is actually due to shaking the camera during shooting.
After shooting, it is possible to correct the sharpness and contrast of the image taken by using retouching software such as Adobe Photoshop Elements on your computer. However, you need to be careful about the correction because over-correction may cause a deterioration of image quality.
It is also possible to adjust the amount of correction by changing the settings of Picture Style of the camera before the image is shot and recorded as a JPEG images.
For more information, please refer to the camera’s instruction manual.
5. Avoid magnifying and printing just an extremely small area of an image taken
Magnifying and printing only an extremely small area of an image taken multiplies slight inaccuracies of focus or the noise of pixels of the image. It is recommended to crop a larger area when cropping the image.